The acute effect of stretching on the passive stiffness of the human gastrocnemius muscle tendon unit

• Published in: The Journal of physiology Vol. 586; no. 1; pp. 97 - 106
• Main Authors: Morse, C. I., Degens, H., Seynnes, O. R., Maganaris, C. N., Jones, D. A.
• Format: Journal Article
• Language: English
• Published: Oxford, UK The Physiological Society 01-01-2008; Blackwell Publishing Ltd; Blackwell Science Inc
• Subjects: Adult; Electromyography; Humans; Male; Muscle Fibers, Skeletal - diagnostic imaging; Muscle Fibers, Skeletal - physiology; Muscle Stretching Exercises; Muscle, Skeletal - diagnostic imaging; Muscle, Skeletal - physiology; Range of Motion, Articular - physiology; Special Section Related Papers; Tendons - diagnostic imaging; Tendons - physiology; Ultrasonography
• ISSN: 0022-3751; 1469-7793
• DOI: 10.1113/jphysiol.2007.140434

Passive stretching is commonly used to increase limb range of movement prior to athletic performance but it is unclear which
component of the muscle–tendon unit (MTU) is affected by this procedure. Movement of the myotendinous junction (MTJ) of the
gastrocnemius medialis muscle was measured by ultrasonography in eight male participants (20.5 ± 0.9 years) during a standard
stretch in which the ankle was passively dorsiflexed at 1 deg s −1 from 0 deg (the foot at right angles to the tibia) to the participants' volitional end range of motion (ROM). Passive torque,
muscle fascicle length and pennation angle were also measured. Standard stretch measurements were made before (pre-) and after
(post-) five passive conditioning stretches. During each conditioning stretch the MTU was taken to the end ROM and held for
1 min. Pre-conditioning the extension of the MTU during stretch was taken up almost equally by muscle and tendon. Following
conditioning, ROM increased by 4.6 ± 1.5 deg (17%) and the passive stiffness of the MTU was reduced (between 20 and 25 deg)
by 47% from 16.0 ± 3.6 to 10.2 ± 2.0 Nm deg −1 . Distal MTJ displacement (between 0 and 25 deg) increased from 0.92 ± 0.06 to 1.16 ± 0.05 cm, accounting for all the additional
MTU elongation and indicating that there was no change in tendon properties. Muscle extension pre-conditioning was explicable
by change in length and pennation angle of the fascicles but post-conditioning this was not the case suggesting that at least
part of the change in muscle with conditioning stretches was due to altered properties of connective tissue.